1. Field of the Invention
The present invention relates to a three-dimensional optical waveguide, a method of manufacturing the same, an optical module, and an optical transmission system for enhancing the performance of an optical device.
2. Related Art of the Invention
Conventionally, when a three-dimensional optical waveguide is formed, for example, in order that light traveling through a waveguide is output vertically with respect to the waveguide, as shown in FIG. 26, a planar filter 1006 such as a wavelength division multiplexing (WDM) filter is inserted in a groove 1002 obliquely formed in a planar waveguide 1001, and the light reflected or transmitted by the planar filter 1006 is oriented with respect to a light receiving element 1008, a lens system and another planar optical waveguide which are disposed spatially, thereby forming the three-dimensional optical waveguide.
However, in such a three-dimensional optical waveguide, spatial adjustment in each waveguide and the lens system is extremely difficult. For example, when a planar wavelength division multiplexing filter is inserted in a planar optical waveguide, it is necessary that the formation of the groove for supporting the wavelength division multiplexing filter be performed extremely precisely. In addition, after the insertion of the wavelength division multiplexing filter into the groove, a precise adjustment for fine positioning of the wavelength division multiplexing filter is further required.
Therefore, when it is intended to enhance the performance by inserting an optical device such as an isolator in such a three-dimensional optical waveguide, since the number of parts requiring adjustment increases, the cost increases.